Whether it’s resistive or capacitive or surface acoustic wave or the new technology that is on such hot products like the iPod, iPhone, and the new iPad, Palm Pre or Microsoft’s Zune; which use projected capacitive touch screen technology in various forms, everyone simply must have touch screen technology on their latest interactive device.
Projected Capacitive technology allows for multiple zones of touch to occur. This can be accomplished due to an invisible grid of sensors on the back of the substrate that map the location of all fingers that come in contact with the screen. The grid pattern detects location of touch by determining relative levels of current within the matrix.
Surface Acoustic Wave technology is the next most advanced technology and is best suited for kiosks ATM’s and Point of Purchase displays. It relies on piezoelectric transmitters and receivers arrayed along the edges of the touch screen. They transmit and receive signals at once, by converting the signal into ultrasonic waves. When you touch the screen, the waves fan out, are absorbed by the array of traces around the perimeter of the screen, and a touch event is directed to the point.
Advantages:Most widely used touch technology
Activation by finger, soft conductive stylus or some gloves
Low Cost and wide range of sizes
Resistive technology offers the durability that – for example - a field tester will need when using an instrument to detect leaks. Much like membrane switches, many of the same ruggedized materials are used in their construction. They hold up well to temperatures between -10º and 60º C. Due to the ITO shield, these touch screens are resistant to shorting or interference as well as chemicals. The screen, while appearing solid, is actually a thin shield with a space between it and the glass. When this durable and conductive ITO shield comes in contact with the glass, the location is noted and a command is executed.
5-Wire Resistive touch screens interact with some form of microprocessor, LCD controller and a graphics chip which renders images on the screen. 5-wire resistive touch screens render the images to the LCD allowing the processor to work harder processing information, especially for hi-use rugged applications. This is because they have a glass substrate suited for more extreme temperatures. Light screens can be added for out door usage. LED back lighting is often used to increase contrast and brighten the graphics.
Advantages:Most widely used touch technology
Activation by finger, stylus pen or gloved hand
Low Cost and wide range of sizes
Surface Capacitive touch screens generally are composed of a scratch resistant top layer, an insulator around the perimeter, a clear anti-glare hard coated layer, then the electrical traces that exit as a connection tail, under this array of traces is the conductive coating, and finally the glass. We choose to reinforce the tail at the conjunction of the traces before their parallel path down the tail. The tail is fitted with a connector each specific controller.
The total thickness can be from 2.0mm to 3.18mm. Polyethylene gasketing is an important part of a touch screen for a rugged application, and can be incorporated to provide NEMA rated protection form dust and liquids, including commonly used chemicals.
Advantages:Withstands contaminants and liquids
Very light force by finger or tethered pen for activation
Extremely fast response to touch time
Touch screens are rapidly being pressed to service in medical technology, form the battlefield to the testing and detection field, in retail banking and sophisticated financial applications, on every form of transportation, and in entertainment and in the gaming industry. Touch screens are part of our daily lives as we make transactions, buy groceries and home improvement products, or travel to our next destination, and continue to be the next destination for designers who develop new products around the world. Sensigraphics is proud to be a part of this growing world-wide creative technology for a new generation of designers.
